Problem: $-\dfrac{8}{2} - \dfrac{2}{4} = {?}$
Solution: $ = - {\dfrac{8 \times 2}{2 \times 2}} - {\dfrac{2 \times 1}{4 \times 1}} $ $ = - {\dfrac{16}{4}} - {\dfrac{2}{4}} $ $ = - \dfrac{{16} - {2}}{4} $ $ = -\dfrac{18}{4}$